The invention relates to an assembly or attachment screw for the pivoting assembly or attachment of at least two horology components, notably two links of a bracelet, for example a watch bracelet. It also relates to a bracelet and, more generally, to a timepiece, such as a wrist watch, both per se, comprising at least one such assembly screw for the pivoting assembly of at least two of their components.
It is known practice to assemble two links of a watch bracelet using a pivoting-guidance pin supported by a screw, the assembled links being able to move rotationally relative to one another. An assembly of this type is exposed to a risk of unwanted unscrewing. This problem, well known to watchmakers, is caused by the repeated movements of the links relative to one another while the bracelet is being worn, or by shoks.
A first solution from the prior art is to use an adhesive, generally referred to as “thread lock”, placed on the threads of an assembly screw in order to reduce the risk of unwanted unscrewing. Such a solution is tricky in practice because it is necessary to master the correct quantity of adhesive. It also demands specialist tooling and a corresponding assembly time. Aftersales service operations are also complex.
Document CH695389 proposes another solution. It describes a device for the pivoting assembly of links of a watch bracelet. This assembly device comprises a screw provided with a head, at one of its ends, and with a threaded part, at its other end. A central part of the screw, cylindrical in shape, acts as a guide pin for the rotational guidance of the central link element. In order to limit the risk of unwanted unscrewing, a tubular cannon made of an elastic material and provided with an annular narrowing is driven into a passage hole in one of the outer link elements, through which passage hole the screw passes, and collaborates with a predetermined portion of the screw. Upon assembly, the screw is introduced into the cannon until the cannon and the screw engage. In the final tightened position, the cannon applies a radial clamping force to the screw which combines with the retention force exerted by the threads of the screw. The screw is thus axially immobilized with respect to the link. Such a solution entails the assembly of several components, which requires a relatively lengthy assembly time. Furthermore, because the clamping force applied by the cannon to the screw has to be high, assembly and/or disassembly operations prove to be difficult.